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IslipWN
Topic Author
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Joined: Mon May 10, 2004 1:05 am

Wing Flexing

Sat May 29, 2004 9:51 am

Please dont think that im stupid for asking this, but why do wings flex on take-off?¿?¿
 
L.1011
Posts: 2172
Joined: Mon Aug 13, 2001 7:46 am

RE: Wing Flexing

Sat May 29, 2004 10:02 am

Weight. The wings hold up the plane, not the body. For a demonstration, put something hard yet flexible over a gap between two desks or something. Push down on the middle of the bridge section. Notice that the edges of the thing barely move, while the middle flexs up and down. On take off, the wings are lifting off, while the fuselage sits like a brick. The wingtips stay steady, while the fuselage stays where it is until the wings pull it up. In the meantime, the difference between the wings (lots of lift) and fuselage (very,very little if any) is increasing, hence the bending.
 
Blackbird1331
Posts: 1741
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RE: Wing Flexing

Sat May 29, 2004 10:23 am

If you want to fully understand the principle, watch a B52 take off. It does not rotate. Its mighty wings "flex" and the fuselage simply lifts into the air in a horisontal attitude.

And please do not ever feel stupid around here, you will learn that you have never learned enough.
Cameras shoot pictures. Guns shoot people. They have the guns.
 
IslipWN
Topic Author
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RE: Wing Flexing

Sat May 29, 2004 10:58 am

thanks so much for the info, ive been wondering for along time.
 
citationjet
Posts: 2569
Joined: Sun Mar 09, 2003 2:26 am

RE: Wing Flexing

Sat May 29, 2004 11:02 am

Actually, the B-52 does not rotate because of the incidence of the wing at the wing root. The wing root incidence is large on the B-52, which means the wing has a higher angle of attack, and therefore doesn't need to "rotate" to take off.
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Blackbird1331
Posts: 1741
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RE: Wing Flexing

Sat May 29, 2004 11:13 am

What? Let's call it AOA. What do you call it, CitationJet? Root canal?
Cameras shoot pictures. Guns shoot people. They have the guns.
 
IslipWN
Topic Author
Posts: 1082
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RE: Wing Flexing

Sat May 29, 2004 11:23 pm

i tried putting a pencil between two desks of mine, and what L.1011 said was true. Thanks .
joe
 
Airtractor
Posts: 26
Joined: Sun Apr 25, 2004 9:36 am

RE: Wing Flexing

Sun May 30, 2004 12:01 am

The only "stupid" question is the one that you keep to yourself !

So remember that your among friends here at A.net and feel free to ask any question you desire a answer for. There is a wealth of knowledge here among members and your welcome to harvest it. Keep it up islipWN !


Cheers

K.M.
In memory of Agnes & Aaron, you're always with me when I fly.
 
USairways16BWI
Posts: 921
Joined: Tue May 11, 2004 4:58 am

RE: Wing Flexing

Sun May 30, 2004 12:10 am

Yes. The wing flexing is the point in which the force of lift is greater than the weight than the plane, and then it takes off. The wings have to bear the weight of the whole plane. Good question IslipWN
 
westindian425
Posts: 729
Joined: Sat May 15, 2004 7:46 am

RE: Wing Flexing

Sun May 30, 2004 12:17 am

Blackbird1331

LOL...Root canal?!  Smile/happy/getting dizzy

Though we understand what CitationJet is saying, there is a difference between the angle of attack and the angle of incidence. The angle of incidence is the angle between the wing chord and a line parallel to the longitudinal axis of the airplane. The angle of attack is the angle between the wing chord and the relative wind.

Neil
God did not create aircraft pilots to be on the ground
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Sun May 30, 2004 3:10 am

Actually, the B-52 does not rotate because of the incidence of the wing at the wing root. The wing root incidence is large on the B-52, which means the wing has a higher angle of attack, and therefore doesn't need to "rotate" to take off

And that is also why B-52's tend to fly with their nose pointed at the ground........seriously.


A wing is there to produce lift. When a wing isn't producing lift, only gravity effects it forcing it down. During takeoff lift is produced, and at a certian point enough is produced the airplane can take-off. But before that point is reached the airplane's wing is producing lift. This lift forces the wing up. The struture takes this upward load and reacts up moving upward itself.

A lot of aircraft with multiple wing tanks will have you use the inboard tanks first and then use the outboard ones, this helps keep the bending forces to a minimum.
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MERSPACE
Posts: 56
Joined: Fri Mar 12, 2004 11:23 am

RE: Wing Flexing

Sun May 30, 2004 3:29 am

It's been my perception that modern airliners--B744, B777, A330/340, etc,
have more wing flex than earlier jets--B742, B707, DC-8.

Are the newer wings more weight optimised, hence slightly thinner wing
skins, hence more flex ? Or is it my imagination ?
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Sun May 30, 2004 3:38 am

Probably, Better materials, more design

The flexing does act as a cushion in turbulence. Just like the shocks in you car cushion against road bumps
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alasdaironeil
Posts: 93
Joined: Wed May 19, 2004 7:29 pm

RE: Wing Flexing

Sun May 30, 2004 3:57 am

The wings are designed to flex during flight. The wings probably flex more today because wings are now made from lighter, thinner, stronger material that can withstand a fair amount of bending.

Also, B747-400 has a longer wing than a B747-200. Also, A340/330 and B777 have very long wingspan:

A330 60.3m
A340-300 60.3m
B747-400 66.4m
B777 60.9m

compared to

B747-200 59.6m
B707 44.4m

If the wing is longer, the wings tend to flex more.

Well, that's what I think anyway

Alasdair
失去在翻譯 - Lost in Translation
 
jadedmonkeys
Posts: 58
Joined: Thu May 27, 2004 8:51 am

RE: Wing Flexing

Sun May 30, 2004 4:08 am

L-188 does that mean, the B-52 has to flare a little higher to get that angle of attack to stall the aircraft for landing?
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Sun May 30, 2004 4:17 am

Actually I don't think they flare it at all.

Most tandem gear setups you have to land flat.

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Blackbird1331
Posts: 1741
Joined: Wed Apr 14, 2004 10:47 am

RE: Wing Flexing

Sun May 30, 2004 4:39 am

Just as a note on the B52. On the Military Av/space forum is a link to a a B52 crash. Just imagine that guy as a flight instructor.It was about thirty topics down on the list. Look for "Spectacular crash of B52".
Cameras shoot pictures. Guns shoot people. They have the guns.
 
MERSPACE
Posts: 56
Joined: Fri Mar 12, 2004 11:23 am

RE: Wing Flexing

Sun May 30, 2004 4:53 am

Thanks for the input's on newer aircraft wing flexing. I knew about
modern alloys being stronger, but I forgot it in my first post.

Watching the wingtips/winglets on a 744 flex upward during takeoff is one of my favorite things.For a fully loaded 744, it seems the flex is in the 10 to 12 foot range. Does anyone know the actual flex on a 744?
 
StanstedFlyer
Posts: 113
Joined: Sat Jul 28, 2001 4:48 pm

RE: Wing Flexing

Sun May 30, 2004 7:21 am

I don't know how far they flex, just that when a 777 I was on took off, I thought the wings were going to snap they flex so far! Seriously... it's quite a sight in heavy turbulence too when they bounce around like mad! I guess it's the skyscraper principle - they flex to go with the stress, otherwise they'd crack!
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Jetfixer75
Posts: 29
Joined: Sun May 16, 2004 2:21 pm

RE: Wing Flexing

Sun May 30, 2004 11:51 am

The total wing flex on a Boeing 744 is 29 ft from top of the deflection to the bottom. I have an actual video of the destructive testing on the 744. When the wing spars finally fail, it sounds like a bomb going off.
 
nudelhirsch
Posts: 1371
Joined: Sun Oct 12, 2003 6:20 am

RE: Wing Flexing

Sun May 30, 2004 2:04 pm

I also think that while the planes rotate the wings do face the major direction of the plane not with the leading edge, but more with the lower surface.
So I guess the air resistance adds to te weight of the plane itself, same during landing. It is less while cruising, because there is "only" the weight...
Putana da Seatbeltz!
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Sun May 30, 2004 2:41 pm

Actually JadedMonkeys, not that I have gotten a nap and thought about it.

The whole reason why Boeing put that large angle of incidence on the aircraft to begin with was because of the landing gear design and it's inablity to handle rotation, either at T/O or landing.

Look at these shots I found.


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Photo © Jukka Huppunen
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Photo © Gordon Zammit



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Photo © Derek Ferguson



About the nose down attitude in flight I mentioned, the USAF has a great publicity shot of a B-1,B-2 and B-52 in formation. You can really tell the differences in attitude to maintain level flight. This is about the best shot of the effect I could find here. The B-1 and the B-52 are flying in formation, so same airspeed and such, Look at how much farther nose down the B-52 has to be to match the B-1


View Large View Medium
Click here for bigger photo!

Photo © AirNikon



The inablity to rotate was handled by other aircraft desingers, including Boeing usually by having a much longer forward strut then aft one, which gave most of them a distinctive nose up appearance when parked.


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Photo © AirNikon
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Photo © Den Pascoe



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Photo © Flavien Breitenmoser
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Photo © Sergey Riabsev



View Large View Medium
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Photo © Pierre-Clément Got
View Large View Medium
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Photo © Joan Martorell


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sovietjet
Posts: 2687
Joined: Sat Mar 15, 2003 12:32 am

RE: Wing Flexing

Sun May 30, 2004 2:48 pm

On the Russian M-4/3M posted above the forward strut actually extends to "rotate" the plane.
 
AirframeAS
Posts: 9865
Joined: Thu Feb 05, 2004 3:56 pm

RE: Wing Flexing

Sun May 30, 2004 3:57 pm

Have you guys seen the destructive testing on the wing of the B777? That was so awesome and very interesting to watch.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Mon May 31, 2004 1:57 pm

Not on the 777.

I have seen video from another Boeing. I think it was the 747-400 when the did the test-to-failure run.

Pretty impressive.

If memory serves the wings on the B-52 will flex 50 feet at the tips in normal operation.
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maiznblu_757
Posts: 4952
Joined: Fri Mar 01, 2002 12:05 pm

RE: Wing Flexing

Mon May 31, 2004 2:01 pm

I just tried an experiment where I was an A380 and a meter stick was the wing.

I put a meter stick, between two desks and tried to stand up on it, the meter stick broke.



[Edited 2004-05-31 07:02:21]
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Mon May 31, 2004 2:07 pm

Now, see if you had used a proper metal yardstick, that wouldn't have happened.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
AirframeAS
Posts: 9865
Joined: Thu Feb 05, 2004 3:56 pm

RE: Wing Flexing

Mon May 31, 2004 2:24 pm

If you want to see the destructive testing on the B777, just get a documentry of the B777 and you'll see how powerful that was. It was fun to watch. I think you can order it off of Boeings website or off of A&E's website.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
Jerry911
Posts: 50
Joined: Wed Jun 19, 2002 12:55 am

RE: Wing Flexing

Mon May 31, 2004 2:33 pm

"watch a B52 take off."

Oh, yeah, we see those all the time.

 Yeah sure
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Wing Flexing

Mon May 31, 2004 2:38 pm

Found the shot I was talking about in post 21

Note how much nose down the B-52 has to fly at in order to maintain the same level flight and speed that the B-1 and the B-2 are flying at.


OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
IslipWN
Topic Author
Posts: 1082
Joined: Mon May 10, 2004 1:05 am

RE: Wing Flexing

Tue Jun 01, 2004 1:16 am

Thanks for all of your responses.
 
jadedmonkeys
Posts: 58
Joined: Thu May 27, 2004 8:51 am

RE: Wing Flexing

Wed Jun 02, 2004 3:39 pm

thanks again L-188 that was very informative and if I had more than 20 post you'd be on my respected list
 
IslipWN
Topic Author
Posts: 1082
Joined: Mon May 10, 2004 1:05 am

RE: Wing Flexing

Thu Jun 03, 2004 6:49 am

thanks everyone for all of your posts.

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